15 ILCS 520/2

All financial institutions in which any such money is deposited shall be required to pay interest. All interest received or paid on account of money in the State Treasury belonging to or for the use of the State so deposited in financial institutions shall be the property of the State of Illinois. If any moneys held by the State Treasurer shall be deposited in financial institutions pursuant to the provisions of this Act, the interest received thereon shall be credited as provided in Section 4.1 of the State Finance Act.